Simethicone
Antacids
Antacids
An antifoaming agent that breaks up gas bubbles in the gut. It eases bloating and gas pain and is often combined with antacids.
Also called: Dimeticone (activated, with silica)
Quick facts
- Group
- Antacids
- Target
- Surface tension of gas bubbles in the gut (no receptor)
- Used for
- Symptoms of gas
- Key effects
- Usually none when used as directed
- Monitor
- Relief of bloating · Red flags that are not simple gas
- ATC
- A03AX13
No doses: the clinician sets them by the current guideline.
Mechanism of action
Simethicone is a silicone surfactant. It lowers the surface tension of gas bubbles trapped in mucus and fluid, so small bubbles merge into larger ones that are passed more easily by belching or flatus. It does not neutralise acid; in antacid mixtures it may reduce foaming and reflux.
- Simethicone lowers gas-bubble surface tension
- Small bubbles merge into larger ones
- Gas is passed more easily; bloating eases
Indications
- Symptoms of gas: pressure, fullness, bloating
- Added to some antacid preparations for reflux symptoms Gastro-oesophageal reflux disease (GERD) →
Adverse effects
Common
- Usually none when used as directed
- Mild stomach upset in some people
Contraindications
- Hypersensitivity to simethicone
Key interactions
- Levothyroxine
- Simethicone can lower levothyroxine absorption; doses are separated
What is monitored
- Relief of bloating
- Red flags that are not simple gas: weight loss, vomiting, blood, severe or persistent pain
Administration and safety
- Chewable tablets are chewed well; liquid drops for infants are measured with the dropper supplied.
- Many products combine simethicone with antacids or loperamide; the label is checked for other active ingredients.
Pregnancy and breastfeeding
Pregnancy data are limited; it is used after checking with a clinician.
Nursing care
- Ask about the pattern of symptoms and alarm features before attributing them to gas.
- In patients on levothyroxine, space the two medicines apart.
- Teach to seek review if pain is severe or persistent, or with vomiting or blood in stool.
Pharmacokinetics
- Absorption
- Acts inside the gut lumen
Test yourself
Think of the answer, then tap the question to see it.
How does simethicone relieve bloating?
It lowers surface tension so small gas bubbles merge and are passed more easily.
Does simethicone neutralise stomach acid?
No; it is an antifoaming agent, often added to antacids.
Which thyroid drug interaction matters?
It can reduce levothyroxine absorption.
Connections
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Simethicone: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.